1. Field of the Invention
The present invention relates to an optical module provided with a surface light emitting type optical element or surface light receiving type optical element, and a method of assembling the optical module.
2. Description of the Related Art
An optical module that is capable of transmitting a plurality of optical signals is provided with a surface light emitting type optical element (it is also called an optical device) such as, for example, an laser diode array, and transmits optical signals emitted from the surface light emitting type optical element to an external circuit, device, apparatus or the like through an optical transmission path or line such as, for example, an optical fiber array. Also, an optical module that is capable of receiving a plurality of optical signals is provided with a surface light receiving type optical element (it is also called an optical device) such as, for example, a photodiode array, and receives optical signals transmitted from an external circuit, device, apparatus or the like through an optical transmission path or line such as, for example, an optical fiber array by the surface light receiving type optical element. There is an optical module that is provided with both a surface light emitting type optical element and a surface light receiving type optical element and is capable of transmitting and receiving a plurality of optical signals.
The optical module capable of transmitting and/or receiving a plurality of optical signals has its optical coupling part that is constructed by a surface light receiving type or surface light emitting type optical element and an optical transmission path or line such as an optical fiber array, and it is required that the optical transmission path, for example, optical fibers of an optical fiber array are mounted on the surface light receiving type or surface light emitting type optical element mounted on a substrate such that the optical fibers are aligned with the optical element.
In a prior art, an optical fiber array has been mounted on a substrate by aligning the cores of the optical fibers of the optical fiber array with the surface light receiving type or surface light emitting type optical element without driving the surface light receiving type or surface light emitting type optical element (this is called “passive alignment”). In other words, the optical fiber array has been mounted on the substrate without conducting active alignment (alignment that is carried out by driving the optical element).
In order to mount the optical fiber array on the substrate without driving the surface light receiving type or surface light emitting type optical element, in a prior art, such a procedure or process has been adopted that some positioning markers are provided on the substrate, for example, and that the optical element and the optical fiber array are mounted on the substrate on the basis of the markers, that is, by use of the markers as their fiducial points, respectively.
However, in case of mounting the optical element and the optical fiber array on the substrate by use of the markers without conducting the active alignment, it is necessary that precise markers are provided on the substrate at high accuracy. Moreover, both the optical element and the optical fiber array must be mounted with respect to the markers at extremely high accuracy. For that reason, in the prior art, a large number of working steps are needed in assembling the optical coupling part of the optical module, which results in a considerable increase of the cost of the optical module.